Stampe SV4-RS: aerobatic icon now a microlight

This is so much aeroplane! In the air, the more you have in front of you, the more it grabs you. Looking at the fuselage, tapering over the engine cowling to the spinner, I check wings-level – where is the horizon and which way are we manoeuvring?

Such visual cues can only be picked up in the rear cockpit. The Stampe’s upper wing is in front of me and the view over the fuel tank in the mid-upper mainplane doesn’t cause me to crane my neck too badly.

Likewise, the rounded wingtips are well forward and I can see what’s coming towards them. While flying over the landscape, dipping a wing is like skiing on freshly fallen snow and gives an unmatched sensation of bonding with my surroundings.

• News: Stampe SV4 microlight coming to UK

How could one possibly think that aeroplanes can fall to Earth? All these things around me are here to keep me aloft – two huge wings providing a total of 18sqm of lift, with the cabanes, struts and flying wires giving noisy reports from the passing airstream.

I’m flying with Raoul Severin from Aachen-Merzbrück, not far from the German-Belgian border. He built this Stampe and, although that sounds simple, the reality is, this machine is a masterpiece. 

The example I’m flying has the same dimensions as the original 1933 aircraft from Stampe & Vertongen but, at 300kg, it weighs only half as much. So under German regulations it’s a microlight – how can that be possible?

“I always wanted to have my own aircraft,” Raoul had told me, “and it had to be a biplane.”

In 2003, Raoul and a friend bought the plans for the Platzer Kiebitz biplane and caught the bug, big time. In 2004, while still a Belgian Air Force pilot, he flew in a Britten-Norman Islander to the Kiebitz fly-in at Riesa. At the event, a number of French enthusiasts asked Raoul if he could supply Kiebitz materials, which he did, and in their wake came no fewer than eight aeroplanes.

However, when he started to offer Kiebitz kits, a dispute arose between himself and designer Michael Platzer, who was also supplying materials to homebuilders. Plainly, things could not continue as they were, so the solution was to use the Kiebitz constructional techniques to create a modern-day SV-4 Stampe.

Stampe made modern

Having bought the Stampe drawings, it took a while for Raoul to thoroughly familiarise himself with the design and make the changes necessary to build it in microlight form. He received help from aerospace engineering students at Aachen Technical University, one of whom was his son, Björn. As part of their diploma studies, the students, three of whom now work regularly part-time for Raoul’s company, Ultralight Concept, did the stress calculations for the engine bearer. Two of them already have a pilot’s licence, while the other is considering training to fly the aeroplane which they helped to develop – surely that would be a dream come true.

We’re a bit to the east of Aachen, sauntering through the air, and I’m highly impressed by the responsiveness of the controls. The four ailerons make themselves felt, and both the elevator and rudder easily put the aircraft in any desired attitude. Sadly, the German regulations prevent aerobatics. Of course, this microlight has much less mass to shift than the original aircraft. There isn’t such a great difference in the speeds, even though the engine only has 80hp, which is 50-to-65hp less than the original. Cruising at 4,700rpm, the ASI reads 70kt. Giving it full power, the Rotax 912 winds up to 5,300rpm and propels the microlight Stampe to 78kt. Due to the fundamental nature of the design, the speed range is, of course, relatively small. We lifted off at 40kt and the best climb was 43kt, and my kneepad approach speed said 48kt.

Even so, the machine is still flying at less than 35kt. I go for the full stall and keep on pulling until the onset, which brings a gentle shake that clearly tells the pilot to go no further. Then it drops the nose, quite slowly, the right wing drops slightly – stick central, recover speed, end of story. No problem, with one exception: the engine doesn’t slow down.

Acoustically, the Rotax whirr, in something which looks so convincingly to be a true veteran aircraft, is a bit like if the famous scenes of the DH Gypsy Moth flying across Kenyan savannah in the film Out of Africa had been scored with techno music…

We’re flying a right-hand circuit and skirt villages, one of the names of which sounds like Oggersheim but is actually Wüselen. Then we return to the airfield, over the A44 autobahn, where Raoul was stationed for almost three years as a helicopter pilot in the 1990s, on the Agusta A109. Did he ever think then that one day he might be landing back at Aachen-Merzbrück in an aeroplane he’d designed and built himself? I keep the question to myself as we’re now just over the threshold, so I should pay attention.

Everything looks right, although the forward view is limited by Raoul’s head, but that doesn’t bother me. However, the touchdown bump comes unexpectedly early. That can be a bit tricky if the pilot has the touchdown seat height estimated from the front cockpit etched on his brain, but finds himself occupying the rear. By my measure, that was a lousy landing, more of an arrival. Of course, the comment from this wordsmith to the expert-on-type has to be the face-saving, “I only wanted to see how much abuse the landing gear could take!” The answer is, plenty.

New versus original

We taxi to the parking area and shut down next to an original Stampe, owned by Detlef Oberbach, who also has his homebuilt Klemm 25 hanging from a roof beam in the hangar. So how would the landing-gear of Detlef’s SV-4B have taken the bump from a landing like that?

The SV-4B’s gear-legs use rubber shock absorbers, not through the strut between the wheel axles and central link under the fuselage, as is the case on the microlight. Compare the two side-by-side, and you’ll spot that the modern SV’s legs are quite a bit lighter-looking. 

Such differences reflect Raoul’s design philosophy, which was never to replicate the original Stampe down to the finest detail. Of course, the overall airframe dimensions had to be correct, 1:1 scale. Likewise, the microlight has the same wing section and even a propeller that’s identical in diameter to the original.

However, the microlight’s construction is quite different. The fuselage is framed from aluminium tubes, joined by pop-riveted aluminium plate fittings, and the empennage is similar. The two-part wings use twin, tubular aluminium spars, wooden primary ribs with secondary ribs in Divinycell hard foam, and are braced with interior steel wires. The upper wing centre-section is steel tube, while the cabanes and wing struts are in profiled aluminium tube, with external steel flying wires.

Dual controls

There are dual controls, with the elevator, frise ailerons and rudder all cable-operated. The profiled aluminium tube undercarriage legs use telescopic spring-struts between the wheel axles and a central linkage under the fuselage. The quad bike tyres on trailer wheels use mountain-bike disc brakes. They’re both operated from the rear cockpit, with a single handbrake on the stick rather than your feet. There’s also a steerable tailwheel coupled to the rudder. In a difference to the original Stampe, the rudder pedals are individuals instead of the one-piece bar. To finish, the SV4-RS is covered with Oratex UL 600 Mk 2 fabric.

All of these changes have been undertaken with the prime aim of keeping the weight down, maintaining a simplicity of construction and ensuring high reliability.

The latter consideration was key in the choice of a modern engine. The Rotax is, quite simply, super-reliable and is an engine everyone knows and can operate. The maintenance and service provisions meet customers’ needs, though the sound of the Rotax can’t match that of the original Renault engine. However, in the SV4-RS the Rotax eliminates a severe handicap, namely that the operation of old aircraft is normally overshadowed by considerable maintenance and unreliability. 

Raoul Severin’s design is damned clever as he’s made use of modern technology, materials and constructional methods which simply didn’t exist when the original Stampe was designed and built. Furthermore, he’s covered the aircraft with Oratex, which is supplied pre-coloured, so requires no dope or paint, and saves between eight and twelve kilos when compared with conventional fabric.

Then there’s the well-tried Kiebitz constructional method, incorporating pre-formed aluminium materials that any homebuilder can work with. Also, the degree of authenticity in recreating the original Stampe form is so great that, when flying the SV4-RS, the pilot can look out and feel like they’re in an original.

Modern microlight, retro charm

In the current range of available retro-look microlights, the SV4-RS is positioned between the Bücker and Funk Jungmann and the Kiebitz. It isn’t so close to the original as Peter Funk’s FK131, who would consider no other engine than the Mikron and, of course, who retained a steel-tube fuselage frame. But nor is it that far away from traditional retro-look biplanes, as is the Kiebitz. Irrespective of that, the microlight Stampe differs from the successful Platzer design in  that you can buy it as a finished aeroplane.

As with the Kiebitz, homebuilders can buy both plans and individual components, but the microlight SV4-RS is also available in kit form. There are three levels of pre-fabricated kits available from Ultralight Concept, ranging from a complete flat-pack of materials (build time estimate 650-1,000hr) to an ultra quick-build with pre-covered fuselage and ready-to-cover wings (200-300hr). Customers can also attend assembly workshop courses, during which they can complete the airframe with the assistance of the company. Correct assembly is guaranteed because Ultralight Concept provides the jigs, which again reduces the costs for the homebuilder. Then there’s the ready-to-fly option, if your country’s regulations allow…

In France and Germany the Stampe has an image which is much the same as that of the Jungmann in Germany, the Tiger Moth in the UK and the Stearman in the USA. However, the SV-4-RS has all the advantages of a modern microlight, such as its Rotax 912 and a ballistic recovery parachute system. It’s an iconic biplane recreated for everyday use, as long as open-cockpit is your thing, and I think that deserves a round of applause.